Cracking of heavy oil vapors



Patented Mar. 20, 1945 UNITED T E PATENT ospice"? 2,371,992 CRACKING OF HEAVY OIL VAPORS Emil Henc, London W.11,'Ilngland No Drawing. Application March 25, 1941, Serial I 9 Claims.

This invention relates to improvements in'and relating to the treatment of heavy oil vapors and it relates more particularly to processes for cracking such vapors at high temperatures and in iron vessels, can be equally well, and-in some respects even In cracking operations it is often'desirable to better achieved by gases or vapors other than produce a maximum of hydrocarbons higher than water, such as for example, hydrocarbons which propylene, the production .of butylene and isohave little tendency to produce carbon under the butylene being particularly desirable, whilst the conditions of th reaction. formation of carbon and asphaltic materials As a result of these observations it was found should be avoid d, that provided the heavy oil vapors were appro- Now it has been stated in literature thatheavy priately diluted with a suitable non-aqueous-, and paraflinic oil vapors can be cracked without carp a y hydrocarbon diluent the amount of bon formation at high temperatures in iron veswater vapor required for purposes of oxidation sels coated with iron oxides, provided the reaction was much less than had hitherto been thought is carried out in the presence of steam, and the necessary Thusrfor x mple, it Was found that minimum proportions of steam which have been when a small percentage of gasolene or s oil mentioned are quite considerable. Was mixed With the heavy Charging Stoc a An investigation of the behaviour of heavy oil addition of only 0.5% or less of water was suflivapors when treated in iron vessels having an cient to give good results. 7 oxidised surface, at high temperatures in the I The effect of these observations will be apparpresence of quantities of water of the ordermenent from the following eXp i n- It can easily tioned in the literature, say from 6%- 10% by be lc lat d that in a ix vap r containin weight of the charging stock has shown that the y weight f wat ap r and 94% y w i ht process when carried out under these conditions of the vapor of an oil of a molecular weight of results in large quantities of ethylene and propylabout e Volume o the aqueous t s ene whilst only small quantities of liquid hydroabout 50% of the total volume, whilst in the case carbons (gasolene) and olefins higher than prof n addition of only 0.5% Weight of water the pylene are formed. Further investigations have Volume dilution is about 7.5%. I shown that by suitably modifying the process re- 0 Whilst t the p e of Water v por i ferred to, and carefully controlling the conditions desirable inorder to ensure the necessary oxidaunder which it is carried out, greatly improved ion ec it has been found tha th qu y results of great industrial utility can be obtained. necessary dilution fi t n e p o u d It is to the results of these further investigand controlled Wi i e essary limits by th tions to be herein described, that the present employment of a suitable non-aqueous diluent invention l t inert as to capability of functioning as an oxidizer It should be stated that the oils used for the and preferably hydrocarbon diluent vapor. investigations were heavy oils, the I. B. P. (initial As a result of all these investigations it has boiling points) of which were higher than 300 40 been found, according to the present invention, C. and that the cracking temperatures used were that heavy oil vapors of an I, B. P. higher than above 600 C, The present invention therefore 300 C. can "be cracked at temperatures above relates mainly, but not necessarily exclusively, to 00 C. in iron vessels coated with iron oxide prosuch oils. vided that at the moment of their entry into the It was found that when used under these concracking plant the heavy oil vapors are diluted ditions water vapor exerts two separate and quite distinct effects. Firstly-it has an oxidising effect on the iron so that any iron formed by the reduction of iron oxide on the vessel by carbon InGreat Britain February 14.

tion of compounds, e. g. ethylene, containing too I few carbon atoms.

It was further found that this dilution effect with a relatively small volumeof an inert vaporous or gaseous diluent, preferably a hydrocarbon, and containing a small volume of one or more gaseous oxidising agents, preferably water vapor.

produced during the reaction is immediately re- 5" It is, of course, preferred to use as a diluent a oxidised. Secondly-it has a diluting effect, hydrocarbon which, under the conditions of the which although of considerable importance must reaction will undergo a favourable change; thus be confined within certain comparatively narrow for example, ethylene will produce propylene and limits. If the dilution is insuflicient there is a higher olefins whilst light paraflins tend to pro tendency for asphaltic substances to be formed duce higher olefins. I from some of the heavy molecules, probably by The reaction mixture is preferably so constipolymerisation, thus leading to the formation of tuted that at the moment of their entry into the more carbon than can satisfactorily be disposed plant the heavy oil vapors are of at least twice of by the iron oxide. If on the other hand the the volume of the diluent, which latter preferably dilution is too great, the splitting of the molecules consists of water vapor and one or more other charging stock, an addition of 0.5% or less bein generally found sufficient. The temperature for the production of gasolene and potential gasolene of high value from heavy oils of an I. B. P. of 300 C. or above is always above 600 C. and gentheoretical considerations on which myinvention is based. Whilst I believe these considerations to be correct, I desire to state that the invention, which consists of the improved process as described, is not limited by any theoretical consideration or explanations.

I claim:

1. A process of cracking vapors of heavy oil comprising diluting said vapors with lighter vaerally lies between 600 and 700 0., the preferred Examples The vapors from a heavy distillate oil (I. B, P. above 300 C.) were treated at substantially atmospheric pressure by being passed through a slightly oxidised iron tube inches long and of 1 inch diameter at temperatures between 660 and 680 C., and in the presence of water vapor in an amount of approximately 0.5% by weight of the oil treated. In Example I no other diluent was used.

Example I.100 ml. of the mixed vapors were passed through the tube at a rate of 2 ml. per minute. Carbon formation was observed and aromatic tarry matter was produced.

Example II.- The same experiment was carried out, but on this occasion 3 litres of ethylene were simultaneously passed through the tube.

No carbon was observed and no aromatic or tarry matter was produced. The only reaction which occurred was a cracking into parafiins of a'molecular weight lower than that of the charging stock, olefins and a small quantity of hydrogen.

Example III.-The same oil as used in the previous two examples, and containing the same amount of water vapor was employed, but instead of diluting the vapors with ethylene, 5% by weight of gasolene and 5% of light gas oil from the original crude oil stock was used. The results obtainedwere'similar to those of Example II.

It should be noted that owing to the tendency for undesired reactions to occur at temperatures below the optimum, it is essential that the mixture to be treated, reach the reaction temperature as rapidly as possible and that the heat required for the reaction be supplied in the shortest possible time. The attainment of this desirable object is facilitated according to the present invention by the reduced amount of water vapor employed. A high proportion of water vapor tends to increase thethickn'ess of the iron oxide coating on the tube or vessel which tends to impede therapid transfer of heat, without increasin the protection of the coating.

In the foregoing I have explained some of. the

porous or gaseous non-aqueous diluent material inert as to capability of functioning as an oxidizer in theprocess and with vaporous or gaseous oxidizer material in a combined or total volume of diluent and oxidizer material not more than half the volume of said heavy oil vapors and in a volume for the oxidizer material less than the volume of the diluent material, and subjecting said thus diluted heavy oil vapors to cracking conditions of temperature and pressure in a reaction chamber having its interior contact surface coated with iron oxide.

2. A process of cracking vapors of heavy oil as defined in claim 1 and in which said oxidizer material comprises water vapor.

3. A process of cracking vapors of heavy oil as defined in claim 1 and in which said diluent material comprises a lighter vaporous or gaseous hydrocarbon than said heavy oil vapors.

4. A process of cracking vapors of heavy oil as defined in claim 1 and in which said diluent material comprises a hydrocarbon productive of an olefin ofgreater number of carbon atoms than said diluent hydrocarbon under said cracking conditions of temperature and pressure to which said heavy oil vapors are subjected.

5. A process of cracking vapors of heavy oil as defined in claim 1 and in which said diluent ma terial comprises a lighter vaporous 0r gaseous hydrocarbon than said heavy oil vapors and water vapor is employed as said oxidizer material.

6. A process of cracking vapors of a heavy oil comprising diluting said vapors with lighter vaporous or gaseous non-aqueous diluent material inert as to capability of functioning as an oxidizer in the process in a weight amount for said diluent material of not more than 10 per cent of the weight of the heavy oil charge from which said heavy oil vapors were formed and with vaporcus or gaseous oxidizer material in a weight amount less than 1 per cent of the weight of said heavy oil charge and subjecting said thus diluted heavy oil vapors to cracking conditions of temperature and pressure in a reaction chamber having its interior contact surface coated with iron oxide.

'7. A process of cracking vapors of a heavy oil as defined in claim 6 and in which water vapor is employed as said oxidizer material.

8. A process of cracking vapors of a heavy oil as defined in claim 6 and in which said diluent material comprises a lighter vaporous or gaseous hydrocarbon than said heavy oil vapors and water vapor is employed as said oxidizer material.

9. A process of cracking vapors of a heavy oil as defined in claim 6 and in which the heavy oil from which said vapors are formed is one having an initial boiling point of not less than 300910. and in which a temperature of not less than 600? C. is employed for the cracking of said heavy oil vapors. v

EMIL HENE. 

